Question

I’m running some JS through googles closure compiler and noticed something about how it handles numbers. It seems that they are converted into something other than base 10 and I can’t figure out what it is.

javascript:(function(){
 var x = 30000;
 console.log(x);
})();

Results in:

(function(){console.log(3E4)})();

How is 3E4 == 30000?

Answer 1

It’s callled Scientific notation, especially the “E notation” part is what you’re after.

Basically, aEb === a * Math.pow(10, b) (though this would be a syntax error – a and b have to be literals, b even has to be an integer).

3 * Math.pow(10, 4) === 30000; // true

The 3 and 4 are just in base 10. This has little to do with bases in fact.